Radio-loud AGN in the XMM-LSS field I. Optical identification and sample selection

C. Tasse, D. Le Borgne, H. Rottgering, P. N. Best, M. Pierre, B. Rocca-Volmerange

Research output: Contribution to journalArticlepeer-review

Abstract

The XMM-Large Scale Structure survey field (XMM-LSS) is an extragalactic window surveyed in the X-ray with the XMM-Newton satellite. It has also been observed in the optical with the Canada-France Hawai Telescope (CFHTLS survey), and in the infrared with the Spitzer Space Telescope (SWIRE survey). These surveys have been carried out to study the structure and evolution of both baryonic and dark matter on cosmological scales. In two previous papers, we presented deep low frequency radio surveys of the XMM-LSS field, with limiting flux density levels of similar to 4 and similar to 1.5 mJy/beam at 325 and 610 MHz respectively (5 sigma). These radio surveys were motivated by the need to understand the various connections between the host galaxies of radio sources and their environments. In this paper, we identify optical counterparts to the low frequency radio sources, using the CFHTLS optical catalogue and images, that have an i-band limiting magnitude of i(AB) similar to 25. We use a likelihood ratio method and estimate that similar to 75% of the radio sources have a detected optical counterpart. Using the CFHTLS and SWIRE data, we derive photometric redshifts for the galaxies that are identified with a radio source, as well as for those that are not; we demonstrate the reliability of these photometric redshifts by deriving the stellar mass function for galaxies at different redshifts, and showing that it is consistent with previous determinations. We classify the radio sources as type-1 AGN, radio galaxies, or star-forming galaxies, and show that the radio luminosity function of the radio galaxies agrees with previous measurements.

Original languageEnglish
Pages (from-to)879-U61
Number of pages54
JournalAstronomy & Astrophysics
Volume490
Issue number3
DOIs
Publication statusPublished - Nov 2008

Keywords

  • methods: observational
  • techniques: photometric
  • galaxies: active
  • galaxies: fundamental parameters
  • cosmology: observations
  • radio continuum: galaxies
  • ACTIVE GALACTIC NUCLEI
  • SCALE STRUCTURE SURVEY
  • GOODS-MUSIC SAMPLE
  • DIGITAL SKY SURVEY
  • LUMINOSITY FUNCTION
  • HOST GALAXIES
  • REDSHIFT
  • GAS
  • SPECTROPHOTOMETRY
  • COUNTERPART

Cite this